SAN DIEGO -- Andres Munoz threw one fastball, and just like that, his legend was born at Petco Park.

The 20-year-old Padres prospect hit 100.6 mph with the first pitch of his big league career, and when the left-field scoreboard lit up with “101,” a restless ballpark came to life. In San Diego, they haven't seen many arms like this one.

Munoz, who was promoted to the big league club on Friday, pitched one inning and threw nine fastballs averaging 100.7 mph in the Padres’ 5-3 loss to the Braves. In the five seasons of Statcast’s existence, only one San Diego pitcher has even thrown a single pitch that fast -- Jose Dominguez in 2016.

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“We’ve known it for a long time,” said Padres manager Andy Green. “It’s a really live arm.”

After a walk to start the sixth inning, Munoz got Austin Riley to bounce into a double play with a heater clocked at 101.9 mph. That’s easily the hardest Padres pitch Statcast has recorded -- a record Munoz probably will break a few times over. He has been clocked above 103 mph in the Minor Leagues.

Munoz’s velocity had everyone in the ballpark buzzing. Except for, well, Munoz. He didn’t seem to care much for the numbers on the scoreboard.

“It was normal,” said Munoz, ranked by MLB Pipeline as the Padres’ No. 18 prospect. “I'm just trying to throw the ball in the zone. That's the biggest thing. I'm never focused on velocity. I'm focused on throwing my pitch and getting it in the zone.”

In that regard, the flame-throwing right-hander got off to an inauspicious start. He threw a first-pitch strike past Nick Markakis. But he followed with four straight balls and his first career walk.

Walks have plagued Munoz throughout his professional career. Before his promotion to Triple-A El Paso earlier this season, he had surrendered more walks than hits. But those control issues have subsided as Munoz has matured. He bounced back nicely Friday night after the walk to Markakis, throwing strikes on six of his next seven pitches.

“It was more about calming the nerves and getting ready,” Munoz said. “I'm not really worried about the velocity. That'll come. That'll always be there.”

The big-time velo isn’t Munoz’s only weapon. He ended the inning by whiffing Brian McCann with a slider for his first Major League strikeout. Two years ago, Munoz’s lack of a legitimate secondary pitch was his most glaring weakness. Now his slider is getting big league whiffs.

“That shows how far he's come,” Green said. “... It's fun watching him get his first punchout -- not on a 101 mph fastball but on a really good slider.”

Still, Munoz’s fastball is clearly his primary weapon, and it came as advertised.

“It's just got life,” said Austin Allen, Munoz’s longtime catcher in the Minor Leagues. “It's very effortless and it comes out of his hand easily. It gets up on hitters like you saw tonight, whether they know it's coming or not. Now that he's got a really good slider, it's going to help his fastball play up.”

If he can limit the walks, Munoz probably has closer-caliber stuff. It’s unclear when he’d be capable of filling that role in San Diego, but a number of people within the organization feel that’s where he’s headed.

Of course, Munoz’s presence might impact some noteworthy decisions regarding the current roster makeup. If the Padres have a closer of the future on board, is there room to deal an established relief ace like Kirby Yates? If not, does it at least make a Craig Stammen trade more palatable?

Those are questions for a different day. Munoz has more to prove before the Padres give him a chance to pitch high-leverage situations. He has thrown only one big league inning, albeit an impressive one.

“His role will evolve in time,” Green said.

For the other 8 1/2 innings Friday night, the Padres were mostly lifeless. Their bats couldn’t elevate against Dallas Keuchel, and Dinelson Lamet surrendered an early three-run homer to Josh Donaldson. Ronald Acuna Jr. mashed a long solo shot in the fifth.

But even in the midst of a disappointing setback, the ballpark came to life in the top of the sixth. When Munoz punched out McCann, he strode toward the dugout to a standing ovation -- a fanbase ready to embrace its newfound fireballer.

“I heard it,” Munoz said. “It was great, it was exciting, it was emotional. After everything, and a good outing, it was exciting coming off the mound hearing that.”

With an electric arm like his, it won’t be the last time Munoz hears it.